Developing And Optimizing On Novel (Oxo)Nitride Phosphors

In the wake of21st century, environment pollution and energy problem become more and more serious, energy saving and environmental protection turn into time’s theme. Energy saving has also attracted more attention in the light and display field, traditional lighting and displaying equipments are abanded, instead, the white LEDs(light-emitting diodes) come to us due to the superior lifetime, efficiency, reliability and low pollution effect.The traditional way generating white light is combining a blue LED chip with YAG:Ce3+yellow phosphor. This way has ten more years’history, but as the LED is applied in large-scale display field, it is not adapt because of its low color rendering index. People tend to use the other two methods:(1) combing an ultravioled (UV) LED with blue, green and red phosphors;(2) using a blue LED to pump green and red phosphors. In these two methods, phosphors used for luminescence convertionare very essential, the quality of phosphors impacts the property of LED device directly. So, development of novel phosphors with easily synthesis, low cost, good properties is one of the important subjects in white LEDs lighting and display field.The requirement of CRI and environment protection becomes higher and higher, oxide and sulfide phosphors can not meet the conditions owning to their unstable chemical properties and single color. Recently,(oxy)nitrides phosphors are very attractive because of their high efficiency, wide range of emission, high chemical and thermal stability. However, few of them can be used in commercial, due to (i) their critical preparation conditions (air-sensitive starting powders high temperature and pressure, etc.);(ii) the lack of general synthesis method. So finding some novel phosphors prepared under soft condition and cost-effective synthetic routes is very necessary and urgent.This dissertation is divided into six chapters:Chapter1introduces the history of artificial light, common used parameter and properties of some representative (oxy)nitrides phosphors. At the end, based on the requirement of science and industrial manufacture, main purpose of this dissertation is put forward.Chapter2is about the experimental procedure and instruments used in synthesis and test. In Chapter3, rare earth doped Ca2AlSi3O2N5and Ca2Si3O2N4phosphors have been synthesized via solid-state reaction. The luminescence properties, sintering temperature, morphology and atmosphere etc. have been studied. Besides, we improve the photoluminescence intensity of Ca2AlSi3O2N5:Eu2+by150%via energy transfer mechanism. Ce3+is used as the sensitizer, and the energy transfer has been demonstrated to be a resonant type via an electric dipole-dipole mechanism and the critical distance has been estimated, which is consistent with that from spectral overlap approach.In Chapter4, Nano-sized Eu doped AlN phosphor powder was successfully synthesized by a metal-organic precursor method. Aluminum and europium chlorides were simultaneously reacted with triethylamine in acetonitrile media to yield solid precipitates, which were transformed into nano-sized AlN:Eu2+phosphor powders upon calcination in an ammonia gas atmosphere. The formation of Al-N bonds through a coordination reaction in solution is a key factor in the formation of well-crystallized AlN:Eu2+grains at a moderately low temperature (1200℃), which significantly suppresses abnormal grain growth and favors the formation of nano-crystalline (～15nm) particles with a homogeneous particle size distribution. The nano-phosphors were effectively excited by UV light and featured an intense green emission band with a peak at506nm.In Chapter5, we reports a cost-effective synthetic route to synthesis red-emitting CaAlSiN3:Eu2+phosphors for white light-emitting diodes. Pure CaAlSiN3:Eu2+phosphors could be achieved at1550℃under NH3atmosphere from CaC2, CaCO3, Si3N4, AlN and Eu2O3starting powders, rather than the air-sensitive starting powders. CaC2was selected as the reduction agent and calcium resource, while the carbon contamination from CaC2was suppressed by the addition of CaCO3and the NH3atmosphere. The obtained CaAlSiN3:Eu2+phosphors are orange in color and emit strong red light under450nm excitation.Chapter6is the conclusion of this dissertation. Besides, we point out something insufficient and development of related direction.